Electrical capacitor and method of making the same



1966 FRIEDRICH GAENGE 3,284,684 ALSO KNOWN As FRITZ GAENGE ELECTRICAL CAPACITOR AND METHOD OF MAKING THE SAME Filed Jan. '7, 1965 FIG! .fizz ezafoz". 750}; kez zye,

United States Patent 6 Claims. Cl. 317-260) The present invention relates to an electrical capacitor, preferably with a dielectric of a thermoplastic material, the plates of which, consisting especially of thin metal layers, produced by vapor treatment, are first contacted by end contact layers of a metal having a high melting temperature upon which is applied a layer of metal having a low melting temperature.

It is a known practice to contact electric capacitors by end contact layers. These end contact layers are usually produced by the so-called Schoops" metal spraying process in which a spraying on of molten metal is effected. There are also known, however, methods of producing end contact layers by other processes as for example, by metal vapor treatment.

It further is a known practice to make the end contact layers not of one metal, but of several metals successively applied to form several layers. It is, for example, a known practice to first apply to the end surfaces a copper layer and only then over such copper layer, to apply low melting metal, for example, zinc.

Through the known processes it is possible to initially achieve a substantially faultless contacting. It was found, how-ever, that especially in the case of end contact capacitors which were constructed of metalized plastic b ands, at a raised temperature there occurred a gradual deterioration of contacting. This impairment is to be explained by the fact that in consequence of shrinkage processes and the like, the contact layer is torn off.

In order to avoid a deterioration of the contacting under the influences of temperature changes there is proposed an electrical capacitor, the plates of which are contacted by end contact layers of a first applied high melting metal on which is superimposed a layer of a low melting metal, in which, according to the invention, the first applied high melting metal is arranged on the ends of the capacitor in the form of individual particles, not forming a cohesive layer, but covering essentially each winding layer of the capacitor.

For the production of the end contact layer according to the invention there is melted into the end surfaces first of all through a short spray burst which may be achieved in the Soho-op process a certain number of particles of a metal with relatively high melting point (ca. 1000* C. and above) and preferably relative high density, such as, for example, gold, copper, cobalt, iron, manganese, nickel, vanadium, zirconium and thereupon there is sprayed on a cohesive layer of a metal with a relatively low melting point such as, for example, zinc or tin or a z'incatin alloy, and to this, in the usual manner, the terminal wires are fastened. In the short spray burst which is necessary for the applying of the particles of the high melting metal, the ends of the capacitor are thermally charged only for such a short time that no damage to the dielectric is to be feared. The non-cohesive particles "ice of the high melting metal act as embedding or anchoring elements for the contact layer subsequently applied to the ends of the wrapped capacitor layers. Although the danger of a thermal damage is considerably less than in the application of a cohesive layer of a high melting metal even if the latter is thin, through the individually applied particles there is achieved a considerably firmer and stronger anchoring of the final end contact layer than would be possible with the aid of cohesive layers. It has proved expedient to select for the particles of the high melting metal, a grain size in the range of 20 microns to 300 microns, preferably 50' to microns.

The utilization of the invention has proved especially advantageous in thin foil capacitors, the dielectric of which consists of thin lacquer layers, in particular, of acetyl cellulose or polystyrene.

In the drawing:

FIG. 1 is an elevational view of a capacitor embodying the invention, with a corner portion broken away; and

FIG. 2 is an enlarged sectional view of the corner portion broken away in FIG. 1.

For the further explanation of the invention, reference is made to FIG. 1 of the drawing in which there is represented a wrapped electric capacitor, the ends of which, as illustrated in FIG. 2, are contacted by first spraying on individual particles 2 of a high-melting metal, for example copper, and subsequently spraying on an end contact layer 3 of a metal with low melting point, for example zinc. Onto the end contact layer 3- there are then soldered the terminal wires 4, by meansof which electrical connections of the capacitor are effected.

Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and desired to have protected by Letters Patent.

What I claim as new and desire to secure by Letters Patent is:

1. An electrical capacitor, with a dielectric of -a thermoplastic material, the plates of which consist of thin metal layers produced by metalization, and are contacted by end contact layers of a first-applied high melting metal and a superimposed layer of a low melting metal, characterized by the feature that the high melting metal, first applied, and directly contacting the capacitor structure is disposed thereon in the form of individual particles which do not form a cohesive layer, but cover essentially each winding layer at the ends of the capacitor, said low melting metal connecting said individual particles and anchoredthereby to the adjacent winding layers.

2. An electrical capacitor is defined in claim 1, wherein the particle size of such high-melting metal is within the range of 20 to 300' microns.

3. An electrical capacitor according to claim 2, wherein the particle size of the high melting metal is within a range of 50 to 150 microns.

4. An electrical capacitor as defined in claim 1, wherein said non-cohesive layer of particles of high melting metal is covered by a cohesive layer of a low melting metal, and terminal, connections secured to said cohesive layer.

5. A process for the production of end contact layers of an electrical capacitor, preferably with a dielectric of a thermoplastic material, the plates of which consist of thin metal layers produced by metalization, and are contacted by end contact layers of a first-applied high melting metal and a superimposed layer of a low melting metal, comprising the steps of first spraying onto the Patented Nov. 8, 1966.

. 3 4 end surfaces of the capacitor with a quantity of individual References Cited by the Examiner particles of a metal having a high melting temperature, UNITED STATES PATENTS with such quantity being less than that required to form a cohesive metal layer, thereby contacting each winding 2,921,246 1/1960 Peck 317260 layer of the capacitor with such individual particles to 5 FO PATENTS form a non-cohesive layer thereof, and thereafter spray- 712 559 7/1954 Great Britain ing on such particle layer a metal having a lower melting point, to form an end contact layer. LEWIS MYERS, Primary Examiner 6. A process as defined in claim 5, wherein said metal having the low melting temperature is applied as a co- 10 ROBERT SCHAEFER Examine"- hesive layer to which terminal connection may be secured. E. GOLDBERG, Assistant Examiner. 

1. AN ELECTRICAL CAPACITOR, WITH A DIELECTRIC OF A THERMOPLASTIC MATERIAL, THE PLATES OF WHICH CONSIST OF THIN METAL LAYERS PRODUCED BY METALIZATION, AND ARE CONTACTED BY END CONTACT LAYERS OF A FIRST-APPLIED HIGH MELTING METAL AND A SUPERIMPOSED LAYER OF A LOW MELTING METAL, CHARACTERIZED BY THE FEATURE THAT THE HIGH MELTING METAL, FIRST APPLIED, AND DIRECTLY CONTACTING THE CAPACITOR STRUCTURE IS DISPOSED THEREON IN THE FORM OF INDIVIDUAL PARTICLES WHICH DO NOT FORM A COHESIVE LAYER, BUT COVER ESSENTIALLY EACH WINDING LAYER AT THE ENDS OF THE CAPACITOR, SAID LOW MELTING METAL CONNECTING SAID INDIVIDUAL PARTICLES AND ANCHORED THEREBY TO THE ADJACENT WINDING LAYERS. 